Arabidopsis thaliana and EcO157 and Se

Many genetic tools are available for studying A. thaliana (thale cress) [174]. Thus, it provides an opportunity to gain insight into the response of a plant to human pathogens. Single strains of EcO157 and Se Newport were assessed in an A. thaliana model for attachment and growth characteristics [175]. In initial experiments, the human pathogens, applied to sterile roots under ideal humidity, remained attached at high concentrations (109 CFU/g tissue) with eventual migration to the stems/shoots (2 x 107 CFU/g). Examination of the roots by confocal microscopy revealed that EcO157-GFP and Se Newport-GFP strains appeared to have "invaded" the plant interior specifically at locations where lateral roots emerge (Figure 2.3C, Figure 2.1H). A similar result was obtained recently with a Se typhimurium strain in an alfalfa seedling model using relatively low numbers of cells (~102 CFU) [120]. Single cells and cell aggregates of EcO157 and Se Newport were observed also on shoots and flowers [175]; surprisingly, EcO157 was isolated also from seed and chaff harvested from contaminated plants, and from plants grown from contaminated seed (unpublished results). The interaction of these two important human pathogens with multiple plant tissues suggests that multiple attachment mechanisms are involved [175].

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